1. Filed of the Invention
The present invention relates to a manufacturing process of a Ni based superalloy, and relates more specifically to a manufacturing process of a Ni based superalloy and a member of the Ni based superalloy, a Ni based superalloy, a member of a Ni based superalloy, a forged billet of a Ni based superalloy, a component of a Ni based superalloy, a structure of a Ni based superalloy, a boiler tube, a combustor liner, a gas turbine blade, and a gas turbine disk achieving both of excellent workability in a manufacturing step of the Ni based superalloy and excellent high temperature strength of the Ni based superalloy.
2. Description of the Related Art
Aiming to improve the efficiency of a gas turbine by raising the combustion temperature, improvement of the heat resistance temperature of gas turbine components has been required. Therefore, with respect to the gas turbine components, as a material excellent in high temperature strength, a Ni based superalloy has been used widely for a turbine disk and blade as well as combustor. The Ni based superalloy achieves excellent high temperature strength by solid solution strengthening effected by adding solid solution strengthening elements such as W, Mo, and Co and precipitation strengthening effected by adding precipitation strengthening elements such as Al, Ti, Nb, and Ta. In the Ni based superalloy of the precipitation strengthening type, the lattice of a γ′ (gamma prime) phase (L12 structure) which is a precipitation strengthening phase precipitates having continuity with a lattice of a γ (gamma) phase (FCC structure, matrix), forms a coherent interface, and thereby contributes to strengthening. Therefore, although the amount of the gamma prime phase just has to be increased in order to improve the high temperature strength, the workability deteriorates as the amount of the gamma prime phase is larger. Accordingly, there are problems that manufacturing of a large forged product becomes harder as the strength of the material becomes higher, and forging cannot be performed due to increase of the defect occurrence rate in forging, and so on.
As a technology for achieving both of the high temperature strength and the hot forgeability of the Ni based superalloy, there is one described in Patent Document 1 (JP-A-2011-052308). In Patent Document 1, a Ni based superalloy is disclosed which contains, in terms of mass, C: 0.001 to 0.1%, Cr: 12 to 23%, Co: 15 to 25%, Al: 3.5 to 5.0%, Mo: 4 to 12%, W: 0.1 to 7.0%, the total of the content of Ti, Ta and Nb is 0.5% or less in terms of mass, and a parameter Ps expressed by an expression (1) (Ps=−7×(C amount)−0.1×(Mo amount)+0.5×(Al amount)) is 0.6 to 1.6.